In a well, such as an oil well, a lost circulation zone is a region in a subterranean formation that inhibits, or prevents, return of mud or other materials following introduction of drilling fluid. For example, during drilling and completion of a well, drilling fluid is introduced into the wellbore. Then, mud and other materials from the wellbore flow back to the surface of the well. However, in a lost circulation zone, the introduction of drilling fluid into the wellbore does not produce a corresponding flow back to the surface of the well.
There can be various causes for lost circulation zones. In some cases, the formation may have high permeability, may have a high porosity and may have a less-than-normal hydrostatic pressure. In some cases, the formation may contain faults, such as fractures, into which the drilling fluid escapes, thereby interrupting the circulation of fluids out of a wellbore. Such lost circulation zones can adversely affect forward drilling operations.
In some cases, in order to continue drilling the well to a target depth or to a next casing point, these lost circulation zones should be remedied. In some cases, lost circulation material (LCM) pills, cement plugs, and X-linked polymer plugs have be used in attempts to remedy lost circulation zones.